U.S. patent number 9,398,378 [Application Number 14/655,486] was granted by the patent office on 2016-07-19 for acoustic generator, acoustic generating apparatus, and electronic apparatus.
This patent grant is currently assigned to Kyocera Corporation. The grantee listed for this patent is KYOCERA Corporation. Invention is credited to Shuichi Fukuoka, Takeshi Hirayama, Noriyuki Kushima, Kentarou Miyazato, Masato Murahashi, Tooru Takahashi.
United States Patent |
9,398,378 |
Miyazato , et al. |
July 19, 2016 |
Acoustic generator, acoustic generating apparatus, and electronic
apparatus
Abstract
An acoustic generator according to an embodiment includes a
film-shaped vibrating body, a flame, and an exciter. The frame is
configured to fix at least both ends of the vibrating body in a
second direction perpendicular to a first direction that is a
thickness direction of the vibrating body. The exciter is disposed
on the vibrating body, and is configured to vibrate itself to
vibrate the vibrating body. The vibrating body has a value of an
average coefficient of linear expansion during a temperature change
from 90.degree. C. to 40.degree. C. set to be not less than a value
of the average coefficient of linear expansion of the vibrating
body during a temperature change from 40.degree. C. to 90.degree.
C., and set to be not less than a value of an average coefficient
of linear expansion of the flame during a temperature change from
90.degree. C. to 40.degree. C.
Inventors: |
Miyazato; Kentarou (Kirishima,
JP), Fukuoka; Shuichi (Kirishima, JP),
Kushima; Noriyuki (Kirishima, JP), Hirayama;
Takeshi (Kirishima, JP), Takahashi; Tooru
(Kagoshima, JP), Murahashi; Masato (Aira,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
KYOCERA Corporation |
Kyoto-shi, Kyoto |
N/A |
JP |
|
|
Assignee: |
Kyocera Corporation (Kyoto-Shi,
Kyoto, JP)
|
Family
ID: |
51021053 |
Appl.
No.: |
14/655,486 |
Filed: |
December 21, 2013 |
PCT
Filed: |
December 21, 2013 |
PCT No.: |
PCT/JP2013/084381 |
371(c)(1),(2),(4) Date: |
June 25, 2015 |
PCT
Pub. No.: |
WO2014/103970 |
PCT
Pub. Date: |
July 03, 2014 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20150358738 A1 |
Dec 10, 2015 |
|
Foreign Application Priority Data
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|
|
|
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Dec 26, 2012 [JP] |
|
|
2012-283051 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04R
7/04 (20130101); H04R 17/00 (20130101); H04R
7/18 (20130101) |
Current International
Class: |
H04R
25/00 (20060101); H04R 17/00 (20060101); H04R
7/04 (20060101); H04R 7/18 (20060101) |
Field of
Search: |
;381/191 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2012-110018 |
|
Jun 2012 |
|
JP |
|
2010/106736 |
|
Sep 2010 |
|
WO |
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2010/131540 |
|
Nov 2010 |
|
WO |
|
Other References
International Search Report, PCT/JP2013/084381, Feb. 4, 2014, 1 pg.
cited by applicant.
|
Primary Examiner: Nguyen; Duc
Assistant Examiner: Nguyen; Sean H
Attorney, Agent or Firm: Volpe and Koenig, P.C.
Claims
The invention claimed is:
1. An acoustic generator, comprising: a film-shaped vibrating body;
a frame configured to fix at least both ends of the vibrating body
in a second direction perpendicular to a first direction that is a
thickness direction of the vibrating body; and an exciter disposed
on the vibrating body, and configured to vibrate itself to vibrate
the vibrating body, wherein the vibrating body has a value of an
average coefficient of linear expansion during a temperature change
from 90.degree. C. to 40.degree. C. set to be not less than a value
of the average coefficient of linear expansion of the vibrating
body during a temperature change from 40.degree. C. to 90.degree.
C., and set to be not less than a value of an average coefficient
of linear expansion of the frame during a temperature change from
90.degree. C. to 40.degree. C., the frame fixes both the ends of
the vibrating body in the second direction and both ends of the
vibrating body in a third direction perpendicular to the first and
second directions, and tension is given to the vibrating body in
both the second and third directions, the tension in the second
direction being different from that in the third direction.
2. The acoustic generator according to claim 1, wherein the
vibrating body has a value of the average coefficient of linear
expansion during a temperature change from 40.degree. C. to
90.degree. C. set to be not more than a value of the average
coefficient of linear expansion of the frame during a temperature
change from 40.degree. C. to 90.degree. C.
3. The acoustic generator according to claim 1, wherein, in a
temperature change of every 10.degree. C. from 90.degree. C. to
40.degree. C., the vibrating body has a value of the average
coefficient of linear expansion set to be not less than a value of
the average coefficient of linear expansion of the frame.
4. The acoustic generator according to claim 1, wherein the
vibrating body is fixed to the frame in a condition of being given
tension thereto.
5. An acoustic generating apparatus, comprising: the acoustic
generator according to claim 1; and an enclosure that surrounds at
least part of at least one of main surface sides of the vibrating
body.
6. An electronic apparatus, comprising: the acoustic generator
according to claim 1; and an electronic circuit connected to the
acoustic generator, the electronic apparatus having a function of
generating sound from the acoustic generator.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is national stage application of International
Application No. PCT/JP2013/084381, filed on Dec. 21, 2013, which
designates the United States, incorporated herein by reference, and
which claims the benefit of priority from Japanese Patent
Application No. 2012-283501, filed on Dec. 26, 2012, the entire
contents of which are incorporated herein by reference.
FIELD
The embodiments disclosed herein relate to an acoustic generator,
an acoustic generating apparatus, and an electronic apparatus.
BACKGROUND
Conventionally, speakers have been known in which a film of a
vibrating body is stretched over a frame and that generate sound by
vibrating the vibrating body using a piezoelectric element attached
to the vibrating body (see Patent Literature 1, for example).
CITATION LIST
Patent Literature
Patent Literature 1: WO 2010/106736 A1
SUMMARY
Solution to Problem
An acoustic generator according to an aspect of embodiments
includes a film-shaped vibrating body, a frame, and an exciter. The
frame is configured to fix at least both ends of the vibrating body
in a second direction perpendicular to a first direction that is a
thickness direction of the vibrating body. The exciter is disposed
on the vibrating body, and is configured to vibrate itself to
vibrate the vibrating body. The vibrating body has a value of an
average coefficient of linear expansion during a temperature change
from 90.degree. C. to 40.degree. C. set to be not less than a value
of the average coefficient of linear expansion of the vibrating
body during a temperature change from 40.degree. C. to 90.degree.
C., and set to be not less than a value of an average coefficient
of linear expansion of the frame during a temperature change from
90.degree. C. to 40.degree. C.
An acoustic generating apparatus according to an aspect of
embodiments includes the acoustic generator and an enclosure. The
enclosure surrounds at least part of at least one of main surface
sides of the vibrating body.
An electronic apparatus according to an aspect of embodiments
includes the acoustic generator and an electronic circuit. The
electronic circuit is connected to the acoustic generator. The
electronic apparatus has a function of generating sound from the
acoustic generator.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a plan view schematically illustrating an acoustic
generator according to a first embodiment.
FIG. 2 is a cross sectional view along line A-A' in FIG. 1.
FIG. 3 is a plan view schematically illustrating an acoustic
generator according to a second embodiment.
FIG. 4 is a cross sectional view along line B-B' in FIG. 3.
FIG. 5 is a perspective view schematically illustrating an acoustic
generating apparatus according to a third embodiment.
FIG. 6 is a block diagram illustrating a configuration of an
electronic apparatus according to a fourth embodiment.
DESCRIPTION OF EMBODIMENTS
Hereinafter, an acoustic generator, an acoustic generating
apparatus, and an electronic apparatus according to embodiments of
the present application are described in detail with reference to
the accompanying drawings. In the drawings, directions are
indicated using x-axis, y-axis, and z-axis that are orthogonal to
each other.
First Embodiment
FIG. 1 is a plan view schematically illustrating an acoustic
generator according to a first embodiment. FIG. 2 is a cross
sectional view along line A-A' in FIG. 1. As illustrated in FIGS. 1
and 2, the acoustic generator in the present embodiment includes an
exciter 1, a vibrating body 3, and frames 5a and 5b.
The vibrating body 3 has a film (membrane) shape and may be formed
using various materials. The vibrating body 3 may be formed using,
for example, a resin such as polyethylene terephthalate (PET) and
polyimide, a metal, paper, or the like. The material for the
vibrating body 3 is, however, selected in consideration of need for
a coefficient of linear expansion of the vibrating body 3 during a
temperature decrease that satisfies a specific relation to be
described later between the coefficient of linear expansion of the
vibrating body 3 during a temperature decrease and a coefficient of
linear expansion of the vibrating body 3 during a temperature
increase/a coefficient of linear expansion of the frames 5a and 5b
during a temperature decrease. Additionally, the vibrating body 3
has a thickness of 10 to 200 .mu.m, for example.
The frames 5a and 5b each have the shape of a "ko" of a Japanese
katakana (the shape of the English alphabet "U") and have a
thickness of about 0.1 mm to 10 mm, for example. Preferably, the
frames 5a and 5b are harder to deform than the vibrating body 3.
Specifically, the frames 5a and 5b preferably have a greater
stiffness and a greater modulus of elasticity than the vibrating
body 3. The frames 5a and 5b may be formed using, for example, a
metal such as stainless steel, a resin, ceramics, glass, or the
like. It is, however, noted that the coefficient of linear
expansion of the vibrating body 3 and the coefficient of linear
expansion of the frames 5a and 5b are required to satisfy the
specific relation to be described later with respect to each other,
so that the material for the frames 5a and 5b is selected in
accordance with the material for the vibrating body 3.
The vibrating body 3 has both ends in the x-axis direction
perpendicular to the z-axis direction that is a thickness direction
thereof fixed to the frames 5a and 5b, so that the vibrating body 3
is vibratably supported by the frames 5a and 5b. The vibrating body
3 has its both ends in the x-axis direction clamped, and fixed with
an adhesive, between the frames 5a and 5b. The vibrating body 3 is
fixed to the frames 5a and 5b in a condition of being given tension
in the x-axis direction. When the frame 5b is not included, the
vibrating body 3 may be bonded to, for example, a surface of the
frame 5a at the positive side in the z direction. When the frame 5a
is not included, the vibrating body 3 may be bonded to, for
example, a surface of the frame 5b at the negative side in the z
direction.
The exciter 1 is a piezoelectric element and is shaped like a plate
having rectangular upper and lower main surfaces (both end faces in
the z-axis direction). Although not illustrated in detail in the
drawings, the exciter 1 includes a laminate body constituted by
alternately laminating piezoelectric body layers formed from
piezoelectric ceramics and internal electrode layers, surface
electrode layers formed on both of the upper and lower surfaces of
the laminate body (both end faces in the z-axis direction), and a
pair of terminal electrodes provided on the respective end faces of
the laminate body in the lengthwise direction (x-axis direction).
The surface electrodes and the internal electrode layers are
alternately drawn from both end faces of the laminate body in the
lengthwise direction (x-axis direction) and are connected to the
corresponding terminal electrodes. Electric signals are applied to
the pair of terminal electrodes through wiring not illustrated.
The exciter 1 is a bimorph piezoelectric element. In response to
input of an electric signal, expansion and contraction are reversed
at a given moment between one side and the other side in the
thickness direction (z-axis direction). The exciter 1 thus bends
and vibrates in the z-axis direction in response to input of an
electric signal. The vibration of the exciter 1 itself causes the
vibrating body 3 to vibrate. The vibration of the vibrating body 3
then generates sound. The exciter 1 may also be a monomorph
vibrating element having a structure in which a piezoelectric
element contracting and expanding to vibrate in response to input
of an electric signal and a metal plate are bonded together, for
example. The main surface of the exciter 1 near the vibrating body
3 is bonded to the vibrating body 3 with a known adhesive such as
an epoxy-based resin, a silicone-based resin, or a polyester-based
resin, a double-faced tape, or the like, for example.
Conventional piezoelectric ceramics, for example, lead zirconate
(PZ), lead zirconium titanate (PZT), or a lead-free piezoelectric
body material such as a Bi-layered compound and a tungsten bronze
structure compound may be used as the piezoelectric body layers of
the exciter 1. The thickness of each of the piezoelectric body
layers is desirably about 10 to 100 .mu.m, for example.
Various known metal materials may be used as the internal electrode
layers of the exciter 1. For example, although the internal
electrode layers may contain a metal component made of silver and
palladium and a material component forming the piezoelectric body
layers, other materials may also be used to form the internal
electrode layers. The surface electrode layers and the terminal
electrodes of the exciter 1 may be formed using various known metal
materials. For example, although the surface electrode layers and
the terminal electrodes may be formed using a material containing a
metal component made of silver and a glass component, other
materials may also be used to form them.
In the acoustic generator in the present embodiment, a value of an
average coefficient of linear expansion of the vibrating body 3
during a temperature change from 90.degree. C. to 40.degree. C. is
set to be not less than a value of the average coefficient of
linear expansion of the vibrating body 3 during a temperature
change from 40.degree. C. to 90.degree. C., and is set to be not
less than a value of an average coefficient of linear expansion of
the frames 5a and 5b during a temperature change from 90.degree. C.
to 40.degree. C. This arrangement allows the vibrating body 3 to be
firmly bonded to the frames 5a and 5b and an acoustic generator
capable of generating sound with favorable sound quality to be
obtained.
The following describes effects from the above. A thermosetting
adhesive or an ultraviolet-curable adhesive is required to firmly
bond the vibrating body 3 to the frames 5a and 5b. Temperature
rises to a point considerably higher than normal temperature when
the adhesive is cured regardless of whether it is the thermosetting
adhesive or the ultraviolet-curable adhesive. Even when the
vibrating body 3 and the frames 5a and 5b are welded together, the
temperature during the welding rises to a level considerably higher
than the normal temperature. An examination conducted by the
inventors has revealed that slackness or wrinkles in the vibrating
body 3 would occur or tension acting on the vibrating body 3 would
reduce in the case where the normal temperature is resumed
following the bonding of the vibrating body 3 to the frames 5a and
5b, which prevents sound having favorable sound quality from
generating. The inventors thus used various materials for the
vibrating body 3 and the frames 5a and 5b and observed conditions
after the bonding. The inventors further studied how each material
underwent expansion and contraction at changing temperatures. It
has, as a result, been known that it is important that the
materials be selected for the vibrating body 3 and the frames 5a
and 5b such that the condition that "the value of the average
coefficient of linear expansion of the vibrating body 3 during the
temperature change from 90.degree. C. to 40.degree. C. is not less
than the value of the average coefficient of linear expansion of
the vibrating body 3 during the temperature change from 40.degree.
C. to 90.degree. C., and is not less than the value of the average
coefficient of linear expansion of the frames 5a and 5b during the
temperature change from 90.degree. C. to 40.degree. C."
(hereinafter referred to as a first condition) is satisfied when
the temperature of the vibrating body 3 and the frames 5a and 5b is
increased from 40.degree. C. to 90.degree. C. and then decreased
from 90.degree. C. to 40.degree. C. It has been then found that
selecting the materials for the vibrating body 3 and the frames 5a
and 5b so as to satisfy the first condition can prevent the
vibrating body 3 from slacking or wrinkling and the tension acting
on the vibrating body 3 from reducing in the case where the normal
temperature is resumed following the bonding of the vibrating body
3 to the frames 5a and 5b and thus can prevent the sound quality
from deteriorating thereby. Reasons why these effects can be
achieved are inferred that a contraction amount of the vibrating
body 3 during the temperature decrease is not less than an
expansion amount during the temperature increase and that the
contraction amount of the vibrating body 3 during the temperature
decrease is not less than a contraction amount of the frames 5a and
5b during the temperature decrease and that the foregoing makes the
slackness in the vibrating body 3 and the reduction in the tension
difficult to occur.
It is noted that, in this description, a term "not less than"
refers to the "equal to" or "greater than", a term "not more than"
refers to the "equal to" or "smaller than". Based on measurement
accuracy of the coefficient of linear expansion, the coefficient of
linear expansion is determined to "be equal" when a deviation is
within .+-.3%. When L.sub.0 is a length at room temperature
(23.degree. C.) and the length changes from L.sub.1 to L.sub.2 with
the temperature changed from T.sub.1 to T.sub.2, the average
coefficient of linear expansion .alpha. is calculated using the
expression (1) given below:
.alpha.=(L.sub.2-L.sub.1)/L.sub.0/(T.sub.2-T.sub.1) (1) To measure
the average coefficient of linear expansion of the vibrating body 3
and the frames 5a and 5b, the measurement sample may be
manufactured by machining the vibrating body 3 and the frames 5a
and 5b or manufactured separately using the same materials as those
used for the frames 5a and 5b and the vibrating body 3.
To satisfy the above-described first condition, the vibrating body
3 is formed using polyimide or PET and the frames 5a and 5b are
formed using stainless steel (SUS301H). Various other combinations
of materials are assumed for the vibrating body 3 and the frames 5a
and 5b to satisfy the first condition. Measurements of coefficients
of linear expansion of a large number of materials are disclosed
and the materials that satisfy the condition can be selected from
among the disclosed materials as appropriate.
Preferably, the acoustic generator in the present embodiment
satisfies, in addition to the above-described first condition, a
condition that "the value of the average coefficient of linear
expansion of the vibrating body 3 during the temperature change
from 40.degree. C. to 90.degree. C. is not more than the value of
the average coefficient of linear expansion of the frames 5a and 5b
during the temperature change from 40.degree. C. to 90.degree. C."
(hereinafter referred to as a second condition). Satisfying the
second condition can further reduce the slackness in the vibrating
body 3 and the reduction in the tension acting on the vibrating
body 3. The reason why these effects can be achieved is inferred
that the slackness in the vibrating body 3 does not tend to occur
in the temperature rising phase, either. It is noted that, to
satisfy both the first condition and the second condition, for
example, the vibrating body 3 may be formed using, polyimide and
the frames 5a and 5b may be formed using stainless steel (SUS301H).
Other combinations may also be used.
Additionally, the acoustic generator in the present embodiment
preferably satisfies, in addition to the above-described first
condition, a condition that "in a temperature change of every
10.degree. C. from 90.degree. C. to 40.degree. C., the value of the
average coefficient of linear expansion of the vibrating body 3 is
not less than the value of the average coefficient of linear
expansion of the frames 5a and 5b" (hereinafter referred to as a
third condition). Specifically, preferably, the value of the
average coefficient of linear expansion of the vibrating body 3
during the temperature change from 90.degree. C. to 80.degree. C.
is not less than the value of the average coefficient of linear
expansion of the frames 5a and 5b during the temperature change
from 90.degree. C. to 80.degree. C.; the value of the average
coefficient of linear expansion of the vibrating body 3 during the
temperature change from 80.degree. C. to 70.degree. C. is not less
than the value of the average coefficient of linear expansion of
the frames 5a and 5b during the temperature change from 80.degree.
C. to 70.degree. C.; the value of the average coefficient of linear
expansion of the vibrating body 3 during the temperature change
from 70.degree. C. to 60.degree. C. is not less than the value of
the average coefficient of linear expansion of the frames 5a and 5b
during the temperature change from 70.degree. C. to 60.degree. C.;
the value of the average coefficient of linear expansion of the
vibrating body 3 during the temperature change from 60.degree. C.
to 50.degree. C. is not less than the value of the average
coefficient of linear expansion of the frames 5a and 5b during the
temperature change from 60.degree. C. to 50.degree. C.; and the
value of the average coefficient of linear expansion of the
vibrating body 3 during the temperature change from 50.degree. C.
to 40.degree. C. is not less than the value of the average
coefficient of linear expansion of the frames 5a and 5b during the
temperature change from 50.degree. C. to 40.degree. C. Satisfying
the third condition can further reduce the slackness in the
vibrating body 3 and the reduction in the tension acting on the
vibrating body 3. The reason why these effects can be achieved is
inferred that the slackness in the vibrating body 3 does not tend
to occur in each condition during the temperature rising phase. It
is noted that, to satisfy both the first condition and the third
condition, the vibrating body 3 may be formed using, for example,
PET and the frames 5a and 5b may be formed using stainless steel
(SUS301H). Other combinations that satisfy the conditions may also
be used.
In the acoustic generator in the present embodiment, the
coefficients of linear expansion of the vibrating body 3 and the
frames 5a and 5b are established as described above and the
vibrating body 3 is fixed to the frames 5a and 5b in a condition of
being given tension in the x-axis direction. These arrangements
allow the tension given to the vibrating body 3 to vary by greatly
changing the temperature of an acoustic generator to provide the
acoustic generator capable of changing the sound quality of the
generated sound by changing the temperature. Additionally, the
arrangements can further reduce the occurrence of the slackness in
the vibrating body 3.
The acoustic generator of the present embodiment can be
manufactured, for example, in the following manner. First of all, a
binder, a dispersant, a plasticizer, and a solvent are added to
powder of a piezoelectric material, and the resultant mixture is
stirred to produce slurry. As the piezoelectric material, any of
lead-based and lead-free materials can be used. Subsequently, a
green sheet is produced by shaping the slurry into a sheet form. A
conductive paste is then printed on the green sheet to form a
conductor pattern serving as an internal electrode. Such green
sheets on which the conductor pattern is formed are laminated on
one another to produce a laminate molded body.
Then, the laminate molded body is degreased, sintered, and cut to
have given dimensions so as to provide a laminate body. The outer
peripheral portion of the laminate body is processed if necessary.
Subsequently, a conductive paste is printed on the main surfaces of
the laminate body in the laminate direction to form conductor
patterns serving as surface electrode layers. A conductive paste is
printed on both side faces of the laminate body in the lengthwise
direction (x-axis direction) to form conductor patterns serving as
a pair of terminal electrodes. The electrodes are then baked at a
given temperature. In this manner, the structure serving as the
exciter 1 can be obtained. Thereafter, in order to give
piezoelectric properties to the exciter 1, a direct-current voltage
is applied thereto through the surface electrode layers or the pair
of the terminal electrodes to polarize the piezoelectric body
layers of the exciter 1. The exciter 1 can be thus prepared.
Then, both ends of the vibrating body 3 in a condition of being
given tension are clamped and fixed between the frames 5a and 5b to
which an adhesive has been applied and are bonded with the frames
with the adhesives being cured. The exciter 1 is bonded to the
vibrating body 3 using an adhesive. In such a manner, the acoustic
generator of the present embodiment can be produced.
Second Embodiment
FIG. 3 is a plan view schematically illustrating an acoustic
generator according to a second embodiment. FIG. 4 is a cross
sectional view along line B-B' in FIG. 3. In the present
embodiment, only differences from the acoustic generator in the
above-described first embodiment are described and the same
reference signs denote the same constituent components and
overlapped description thereof is omitted.
As illustrated in FIGS. 3 and 4, the acoustic generator in the
present embodiment includes frames 6a and 6b in place of the frames
5a and 5b. The acoustic generator in the present embodiment further
includes a resin layer 20.
The frames 6a and 6b each have a rectangular frame shape. A
vibrating body 3 has a peripheral edge portion of its rectangular
shape, the entire peripheral edge portion being clamped and fixed
generally between the frames 6a and 6b in a condition of being
given tension in a planar direction (the x-axis direction and the
y-axis direction). The vibrating body 3 is vibratably supported by
the frames 6a and 6b. The material for the frames 6a and 6b is
selected in a manner similar to that used when the material for the
frames 5a and 5b in the acoustic generator in the above-described
first embodiment is selected. The shape of the frames 6a and 6b is
not limited to the rectangle and may be a circle or a rhombus.
The resin layer 20 fills all over the inner side of the frame 6a
such that an exciter 1 is buried therein. The resin layer 20 can be
formed using various known materials. For example, resins such as
acrylic-based resins and silicone-based resins, rubber, or the like
can be used. For example, Young's modulus is desirably in a range
of 1 MPa to 1 GPa. The thickness of the resin layer 20 is desirably
the thickness with which the exciter 1 is completely covered in
terms of spurious reduction, but is not limited thereto. A given
advantageous effect can be achieved when at least part of the
vibrating body 3 is covered.
The acoustic generator in the present embodiment having the
arrangements as described above can also achieve the similar
effects as those achieved by the acoustic generator in the
above-described first embodiment when the vibrating body 3 and the
frames 6a and 6b are selected so as to satisfy conditions similar
to the above-described first through third conditions.
Specifically, by selecting the materials for the vibrating body 3
and the frames 6a and 6b so as to satisfy a condition that "the
value of the average coefficient of linear expansion of the
vibrating body 3 during the temperature change from 90.degree. C.
to 40.degree. C. is not less than the value of the average
coefficient of linear expansion of the vibrating body 3 during the
temperature change from 40.degree. C. to 90.degree. C., and is not
less than the value of the average coefficient of linear expansion
of the frames 6a and 6b during the temperature change from
90.degree. C. to 40.degree. C." (hereinafter referred to as a
fourth condition), the acoustic generator in the present embodiment
can prevent the slackness in the vibrating body 3 and the reduction
in the tension acting on the vibrating body 3 and can prevent
aggravation of the sound quality thereby.
Additionally, by selecting the materials for the vibrating body 3
and the frames 6a and 6b so as to satisfy, in addition to the
fourth condition, a condition that "the value of the average
coefficient of linear expansion of the vibrating body 3 during the
temperature change from 40.degree. C. to 90.degree. C. is not more
than the value of the average coefficient of linear expansion of
the frames 6a and 6b during the temperature change from 40.degree.
C. to 90.degree. C." (hereinafter referred to as a fifth
condition), the acoustic generator in the present embodiment can
further reduce the slackness in the vibrating body 3 and the
reduction in the tension acting on the vibrating body 3.
Additionally, by selecting the materials for the vibrating body 3
and the frames 6a and 6b so as to satisfy, in addition to the
fourth condition, a condition that "in a temperature change of
every 10.degree. C. from 90.degree. C. to 40.degree. C., the value
of the average coefficient of linear expansion of the vibrating
body 3 is not less than the value of the average coefficient of
linear expansion of the frames 6a and 6b" (hereinafter referred to
as a sixth condition), the acoustic generator in the present
embodiment can further reduce the slackness in the vibrating body 3
and the reduction in the tension acting on the vibrating body
3.
In the acoustic generator in the present embodiment, the vibrating
body 3 has both ends in the y-axis direction fixed to the frames 6a
and 6b, in addition to having both ends in the x-axis direction
fixed thereto. This arrangement allows the number of resonances in
vibrations of the vibrating body 3 to be increased, so that the
resonance frequency is dispersed in the use frequency band. This
allows sound pressure of the sound generated by the acoustic
generator to have flat and favorable frequency characteristics.
In the acoustic generator in the present embodiment, tension is
given in both the x-axis direction and the y-axis direction. Thus,
selecting the vibrating body 3 and the frames 6a and 6b so as to
satisfy at least the fourth condition allows the tension in both
the x-axis direction and the y-axis direction given to the
vibrating body 3 to be changed by greatly changing the temperature
of the acoustic generator. An acoustic generator capable of further
changing the sound quality of the generated sound through the
change in the temperature can thus be obtained.
In the acoustic generator in the present embodiment, the tension in
the x-axis direction may be made different from that in the y-axis
direction. Specifically, having the tension in the x-axis direction
made different from that in the y-axis direction to thereby change
a ratio of the tension in the x-axis direction to that in the
y-axis direction allows a condition in which the resonance
frequency is distributed among different resonance modes in the
vibration of the vibrating body 3 to vary. Thus, the resonance
frequency can be more uniformly dispersed in the use frequency
band. The sound pressure of the sound generated by the acoustic
generator thus can have flatter and more favorable frequency
characteristics.
Additionally, having the tension in the x-axis direction made
different from that in the y-axis direction and selecting the
vibrating body 3 and the frames 6a and 6b so as to satisfy at least
the fourth condition enable the acoustic generator in the present
embodiment to be capable of variously setting the change in sound
quality to the change in temperature.
Third Embodiment
FIG. 5 is a perspective view schematically illustrating an acoustic
generating apparatus according to a third embodiment. The acoustic
generating apparatus in the present embodiment includes, as
illustrated in FIG. 5, an acoustic generator 31 and an enclosure
32.
The acoustic generator 31 generates sound (including sound out of
an audible frequency band) in response to an input of a sound
signal. The acoustic generator 31, although not elaborately
illustrated, represents the acoustic generator in the
above-described second embodiment.
The enclosure 32 is shaped into a box-like rectangular
parallelepiped. The enclosure 32 has at least one opening. The
acoustic generator 31 is attached so as to close the opening. The
enclosure 32 is formed so as to surround a main surface of the
vibrating body 3 on the side on which the exciter 1 is disposed. It
is noted that the enclosure 32 is formed so as to surround at least
part of at least one main surface of the vibrating body 3. Thus,
the shape of the enclosure 32 is not limited to the rectangular
parallelepiped. The enclosure 32 may be shaped into, for example, a
cone, a sphere, or the like. Additionally, the enclosure 32 does
not need to have a box shape. The enclosure 32 may be shaped into a
flat plate or the like. The enclosure 32 may have a function of
reducing sound in reverse phase generated from a back surface of
the acoustic generator 31 and sneaking thereinto or a function of
internally reflecting sound generated by the acoustic generator 31.
The enclosure 32 can be formed using various known materials. For
example, the enclosure 32 may be formed using such materials as
wood, synthetic resins, and metals.
The acoustic generating apparatus in the present embodiment
generates sound using the acoustic generator 31 configured with the
acoustic generator in the above-described second embodiment, and
thus can generate sound having favorable sound quality. The
acoustic generating apparatus in the present embodiment, including
the enclosure 32, can also generate sound having more favorable
sound quality than by the acoustic generator 31. It is noted that
the acoustic generator in the first embodiment, instead of the
acoustic generator in the second embodiment, may be incorporated to
achieve the similar effects. Alternatively, a similar acoustic
generator according to another embodiment may still be
incorporated.
Fourth Embodiment
FIG. 6 is a block diagram illustrating a configuration of an
electronic apparatus 50 according to a fourth embodiment. As
illustrated in FIG. 6, the electronic apparatus 50 of the present
embodiment includes an acoustic generator 30, an electronic circuit
60, a key input unit 50c, a microphone input unit 50d, a display
unit 50e, and an antenna 50f. FIG. 6 is a block diagram of an
electronic apparatus that is assumed to be, for example, a mobile
phone, a tablet terminal, or a personal computer.
The electronic circuit 60 includes a control circuit 50a and a
communication circuit 50b. The electronic circuit 60 is connected
to the acoustic generator 30 and has a function to output a sound
signal to the acoustic generator 30. The control circuit 50a is a
control unit of the electronic apparatus 50. The communication
circuit 50b, for example, transmits and receives data through the
antenna 50f on the basis of the control by the control circuit
50a.
The key input unit 50c is an input device of the electronic
apparatus 50 and accepts a key input operation performed by an
operator. The microphone input unit 50d is also an input device of
the electronic apparatus 50 and accepts a sound input operation
performed by an operator. The display unit 50e is a display output
device of the electronic apparatus 50 and outputs display
information on the basis of the control by the control circuit
50a.
The acoustic generator 30 is an acoustic generator as described in
the first or the second embodiments. The acoustic generator 30
functions as an acoustic output device in the electronic apparatus
50. The acoustic generator 30 generates sound (including sound out
of an audible frequency band) in response to a sound signal input
from the electronic circuit 60. The acoustic generator 30 is
connected to the control circuit 50a of the electronic circuit 60
and generates sound when a voltage controlled by the control
circuit 50a is applied thereto.
As described above, the electronic apparatus 50 in the present
embodiment includes at least the acoustic generator 30 and the
electronic circuit 60 connected to the acoustic generator 30 and
has a function of generating sound from the acoustic generator 30.
The electronic apparatus 50 in the present embodiment as described
above, because the electronic apparatus 50 generates sound using
the acoustic generator 30 according to the above-described first or
second embodiment, can generate sound having favorable sound
quality.
As an example of the configuration of the electronic apparatus 50,
the housing of the electronic apparatus 50 may include therein the
electronic circuit 60, the key input unit 50c, the microphone input
unit 50d, the display unit 50e, the antenna 50f, and the acoustic
generator 30, which are illustrated in FIG. 6. As another example
of the configuration of the electronic apparatus 50, an apparatus
main body including the electronic circuit 60, the key input unit
50c, the microphone input unit 50d, the display unit 50e, and the
antenna 50f, which are illustrated in FIG. 6, in the housing is
connected to the acoustic generator 30 in such a manner that they
can transmit electric signals through a lead wire or the like.
The electronic apparatus of the present embodiment does not need to
include all of the key input unit 50c, the microphone input unit
50d, the display unit 50e, and the antenna 50f, which are
illustrated in FIG. 6, and may include at least the acoustic
generator 30 and the electronic circuit 60. The electronic
apparatus 50 may also include other constituent components.
Furthermore, the electronic circuit 60 is also not limited to the
configuration of the electronic circuit 60 described above and may
be an electronic circuit having another configuration.
The electronic apparatus of the present embodiment is not limited
to the above-mentioned electronic apparatus such as a mobile phone,
a tablet terminal, or a personal computer. In various types of
electronic apparatuses having a function to generate sound or
voice, such as a television, audio equipment, a radio, a vacuum
cleaner, a washing machine, a refrigerator, and a microwave oven,
the acoustic generator 30 as described in the first or the second
embodiments can be used as an acoustic generating apparatus.
Modification
The present disclosure is not limited to the above-mentioned
embodiments, and various changes or improvements can be made in a
range without departing from a concept of the invention.
For example, although an example in which a single exciter 1 is
attached to the surface of the vibrating body 3 is described in the
above-described embodiments so as to simplify the drawings, the
embodiments are not limited thereto. For example, a larger number
of exciters 1 may also be attached onto the surface of the
vibrating body 3. Alternatively, for example, the exciter 1 and/or
the resin layer 20 may be provided at both surfaces of the
vibrating body 3.
Although an example in which a piezoelectric element is used as the
exciter 1 is described in the above-described embodiments, the
embodiments are not limited thereto. The exciter 1 only has to have
a function to change electric signals into mechanical vibration,
and other devices having a function to change electric signals into
mechanical vibration may also be used as the exciter 1. For
example, an electrodynamic exciter, an electrostatic exciter, and
an electromagnetic exciter that have been known as exciters
vibrating a speaker may be used as the exciter 1. The
electrodynamic exciter applies an electric current to a coil
arranged between magnetic poles of a permanent magnet to vibrate
the coil. The electrostatic exciter applies a bias and an electric
signal to two opposing metal plates to vibrate the metal plates.
The electromagnetic exciter applies an electric signal to a coil to
vibrate a thin iron plate.
Example
The following describes an example of the present disclosure. The
acoustic generator according to the second embodiment illustrated
in FIGS. 3 and 4 was manufactured and characteristics thereof were
evaluated.
First of all, powder of a piezoelectric material containing lead
zirconium titanate (PZT) obtained by substituting part of Zr with
Sb, a binder, a dispersant, a plasticizer, and a solvent were
kneaded through ball mill blending to produce slurry. Subsequently,
through a doctor blade method, a green sheet was produced from the
obtained slurry. A conductive paste containing Ag and Pd was
applied to the green sheet by screen printing and a conductor
pattern having a predetermined shape was thereby formed as an
internal electrode layer. The green sheet on which the conductor
pattern was formed and other green sheets were laminated one on top
of another and were pressurized to produce a laminate molded body.
The laminate molded body was degreased at 500.degree. C. for one
hour in the atmosphere; thereafter, the laminate molded body was
sintered at 1100.degree. C. for three hours in the atmosphere to
obtain a laminate body.
Then, both end faces in the obtained longitudinal direction of the
laminate body were cut by dicing to thereby expose a leading end of
the internal electrode layer on a side surface of the laminate
body. A conductive paste containing Ag and glass was applied by
screen printing to the main surfaces on both sides of the laminate
body to form surface electrode layers. The conductive paste
containing Ag and glass was thereafter applied by dipping to both
side surfaces in the longitudinal direction of the laminate body
and was baked in the atmosphere at 700.degree. C. for ten minutes
to form terminal electrodes. The laminate body was thus produced.
The produced laminate body had a width of 18 mm, a length of 46 mm,
and a thickness of 0.1 mm. Polarization was subsequently performed
by application of a voltage of 100 V through the terminal
electrodes for two minutes to thereby obtain the exciter 1 as a
bimorph laminated piezoelectric element.
Four types of resin films of polyimide, polyethylene terephthalate
(PET), polyethylene naphthalate (PEN), and nylon were prepared for
the vibrating body 3. Thickness was set to 0.025 mm. Stainless
steel (SUS301H) having a thickness of 0.5 mm was used for each of
the frames 6a and 6b. The frames 6a and 6b each have inside
dimensions of 100 mm in length and 70 mm in width.
Subsequently, the peripheral edge portions of the vibrating body 3
to which tension was given were clamped and fixed by the frames 6a
and 6b to which an adhesive was applied and were bonded with the
frames with the adhesive being cured. The exciter 1 was bonded to
one of the main surfaces of the vibrating body 3 using an adhesive
and a conductive wire was joined to wire the exciter 1. The inside
of the frame 6a was filled with an acrylic-based resin until the
acrylic-based resin was flush with the frame 6a. The acrylic-based
resin was then solidified to form the resin layer 20. The acoustic
generator illustrated in FIGS. 3 and 4 was thus manufactured and
the sound quality of the sound generated by the acoustic generator
was evaluated.
Samples composed of the same materials as those used for the frames
6a and 6b and the four types of resin films mentioned above were
manufactured for measuring the average coefficients of linear
expansion and the average coefficients of linear expansion were
measured. A TAS-200 manufactured by Rigaku was used as the
measuring system. The temperature increase and decrease rates were
3.degree. C./min., respectively. The samples had the following
dimensions: SUS301H has a length of 10 mm, a width of 4 mm, and a
thickness of 1 mm; and polyimide, PET, PEN, and nylon each has a
length of 10 mm, a width of 4 mm, and a thickness of 0.025 mm.
Measurements were taken under a condition with a compression load
of 0.196 N being applied to SUS301H and a tensile load of 0.087 N
being applied to polyimide, PET, PEN, and nylon. The ambience was
air. Table 1 illustrates evaluation results of the sound quality
and the average coefficients of linear expansion. In Table 1, the
average coefficients of linear expansion are in units of
10.sup.-6/K.
TABLE-US-00001 TABLE 1 Frame Vibrating body SUS301H Polyimide PET
PEN Nylon Average 17.1 12.7 22.2 2.4 -1.5 coefficient of linear
expansion (40.degree. C. .fwdarw. 90.degree. C.) Average 19.2 24.3
28.0 12.3 17.6 coefficient of linear expansion (90.degree. C.
.fwdarw. 40.degree. C.) Sound quality -- .largecircle.
.largecircle. X X
The measurements of the average coefficients of linear expansion
revealed that, when SUS301H was used as the material for the frames
6a and 6b, use of polyimide or PET as the material for the
vibrating body 3 satisfied the fourth condition that "the value of
the average coefficient of linear expansion of the vibrating body 3
during the temperature change from 90.degree. C. to 40.degree. C.
is not less than the value of the average coefficient of linear
expansion of the vibrating body 3 during the temperature change
from 40.degree. C. to 90.degree. C., and is not less than the value
of the average coefficient of linear expansion of the frames 6a and
6b during the temperature change from 90.degree. C. to 40.degree.
C.". The fourth condition was not satisfied when PEN or nylon was
used as the material for the vibrating body 3.
The measurements of the average coefficients of linear expansion
revealed that, when SUS301H was used as the material for the frames
6a and 6b, use of polyimide as the material for the vibrating body
3 satisfied the fifth condition that "the value of the average
coefficient of linear expansion of the vibrating body 3 during the
temperature change from 40.degree. C. to 90.degree. C. is not more
than the value of the average coefficient of linear expansion of
the frames 6a and 6b during the temperature change from 40.degree.
C. to 90.degree. C.", in addition to the fourth condition. Neither
the fourth condition nor the fifth condition were satisfied when
PET, PEN, or nylon was used as the material for the vibrating body
3.
The measurements of the average coefficients of linear expansion
revealed that, although not illustrated in Table 1, when SUS301H
was used as the material for the frames 6a and 6b, use of PET as
the material for the vibrating body 3 satisfied the sixth condition
that "in a temperature change of every 10.degree. C. from
90.degree. C. to 40.degree. C., the value of the average
coefficient of linear expansion of the vibrating body 3 is not less
than the value of the average coefficient of linear expansion of
the frames 6a and 6b", in addition to the fourth condition. Neither
the fourth condition nor the sixth condition were satisfied when
polyimide, PEN, or nylon was used as the material for the vibrating
body 3.
The evaluation results of the sound quality revealed that, when
SUS301H was used as the material for the frames 6a and 6b, use of
polyimide or PET as the material for the vibrating body 3 obtained
sound having a sufficiently favorable sound quality. Use of PEN or
nylon as the material for the vibrating body 3 failed to obtain
sound having a favorable sound quality. When PEN or nylon was used
as the material for the vibrating body 3, wrinkles were observed in
the vibrating body 3.
Additional advantages and modifications will readily occur to those
skilled in the art. Therefore, the invention in its broader aspects
is not limited to the specific details and representative
embodiments shown and described herein. Accordingly, various
modifications may be made without departing from the spirit or
scope of the general inventive concept as defined by the appended
claims and their equivalents.
* * * * *